<!DOCTYPE html>
<html>

<head lang="en">
  <meta charset="UTF-8">
  <title></title>
  <style type="text/css">
    .small {

      background: green;
      width: 100px;
      height: 100px;
    }

    .box {
      width: 100px;
      height:100px;
      background: blue;
      padding: 150px 150px;
    }
  </style>

</head>

<body>

  <div class="box">
    <div class="small">
      盒子模型
    </div>
  </div>


</body>
</html>
